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Title |
Page |
| TU2001 |
The 12-GeV CEBAF Upgrade Project
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218 |
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- A. Freyberger, J. F. Benesch, S. A. Bogacz, Y.-C. Chao, J. M. Grames, L. Harwood, R. Kazimi, G. A. Krafft, L. Merminga, E. Pozdeyev, Y. Roblin, M. Spata, M. Wiseman, B. C. Yunn, Y. Zhang
Jefferson Lab, Newport News, Virginia
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The status of the CEBAF recirculating linac upgrade from 6 GeV to 12 GeV is presented. This upgrade consists of an increase in machine energy by a factor of two and the addition of a new experimental hall [including new extraction region and transport line]. The doubling of the energy will be achieved by three means: added new high-gradient 7-cell cryomodules, refurbishment of existing cryomodules, and adding an extra pass through the linac. Beam requirements, beam physics issues including synchrotron radiation effects, and the expected beam properties will be presented. The talk will also present the beam optics for the 12 GeV upgrade including optimization of multipass transport in the linacs.
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| MOP057 |
A Fault Recovery System for the SNS Superconducting Cavity Linac
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174 |
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- J. Galambos, S. Henderson, Y. Zhang
ORNL, Oak Ridge, Tennessee
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One of the advantages for the change of the Spallation Neutron Source (SNS) linac from copper to superconducting cavities, was the possibility of fault tolerance. Namely, the ability to rapidly recover from a cavity failure, retune the downstream cavities with minimal user disruption. While this is straightforward for electron machines, where beta is constant, it is more involved for the case of proton machines, where the beta changes appreciably throughout the Superconducting Linac (SCL). For SNS when the SCL is first turned on, each cavity’s RF amplitude and phase (relative to the beam) are determined with a beam based technique. Using this information a model calculated map of arrival time and phase setpoint for each cavity is constructed. In the case of cavity failure(s) the change in arrival time at downstream cavities can be calculated and the RF phases adjusted accordingly. Typical phase adjustments are in the 100 – 1000 degree range. This system has been tested on the SNS SCL in both controlled tests and a need based instance in which more than 10 cavity amplitudes were simultaneously reduced. This scheme and results will be discussed.
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| TUP032 |
Comparison of SNS Superconducting Cavity Calibration Methods
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315 |
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- Y. Zhang, I. E. Campisi, P. Chu, J. Galambos, S. Henderson, D.-O. Jeon, K.-U. Kasemir, A. P. Shishlo
ORNL, Oak Ridge, Tennessee
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Three different methods have been used to calibrate the SNS superconducting cavity RF field amplitude. Two are beam based and the other strictly RF based. One beam based method uses time-of-flight signature matching (phase scan method), and the other uses the beam-cavity interaction itself (drifting beam method). Both of these methods can be used to precisely calibrate the pickup probe of a SC cavity and determine the synchronous phase. The initial comparisons of the beam based techniques at SNS did not achieve the desired precision of 1% due to the influence of calibration errors, noise and coherent interfaces in the system. To date the beam-based SC cavity pickup probe calibrations agree within approximately 4%, comparable to the conventional RF calibrations.
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| TUP071 |
Beam-Loading Effects on Phase Scan for the Superconducting Cavities
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418 |
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- D.-O. Jeon, S. Henderson, S.-H. Kim, Y. Zhang
ORNL, Oak Ridge, Tennessee
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When the beam is passing through superconducting cavities, it excites beam induced field in cavities. A systematic study was performed to study the beam loading effects by the nonrelativistic beam for β = 0.81 superconducting cavities of the SNS linac. The analysis indicates that the induced field level is quite close to the estimation and its effect on the phase scan is consistent with the model.
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| TUP073 |
Simulations of RF Errors in the SNS Superconducting Linac
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423 |
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- Y. Zhang, S. Henderson
ORNL, Oak Ridge, Tennessee
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Minimizing beam emittance growth in the SNS superconducting linac due to RF errors, either correlated or uncorrelated, is essential since it can lead to beam loss in the linac and in the downstream ring. From multi-particle simulation studies of both matched and mismatched linac lattices, for the design peak beam current of 38 mA, as well as a typical commissioning beam current of 20 mA, we conclude that the linac may tolerate much higher non-correlated RF errors, especially in the second half of the superconducting linac, where errors in synchronous phase up to 10 degrees and that of cavity field amplitude up to 10% is acceptable. However, tolerance to correlated RF errors in the linac is within only 0.5 degree and 0.5 %, from simulations using a simple longitudinal linac model. Beam parameter measurement results acquired during linac beam commissioning confirmed the simulations.
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| TUP084 |
Drifting Beam Application for SNS Superconducting Cavity Setting
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454 |
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- P. Chu, Y. Zhang
ORNL, Oak Ridge, Tennessee
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A software application for tuning superconducting linac cavity has been developed and tested at the Spallation Neutron Source (SNS). The application is based on the drifting beam method and the XAL online model. The drifting beam method and the application were proved to be consistent with other cavity tuning method during the SNS commissioning runs. Detail algorithm and data acquisition for the application will be presented.
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